Cretaceous

Definitions

from The American Heritage® Dictionary of the English Language, 4th Edition

adj. Of or belonging to the geologic time, system of rocks, and sedimentary deposits of the third and last period of the Mesozoic Era, characterized by the development of flowering plants and ending with the sudden extinction of the dinosaurs and many other forms of life. See Table at geologic time.

adj. Of, containing, or resembling chalk.

n. The Cretaceous Period or its system of deposits.

from Wiktionary, Creative Commons Attribution/Share-Alike License

proper n. The geologic period within the Mesozoic era that comprises lower and upper epochs from about 146 to 65 million years ago

from the GNU version of the Collaborative International Dictionary of English

adj. Having the qualities of chalk; abounding with chalk; chalky. See chalk.

adj. Of, pertaining to, or designating, the period of time following the Jurassic and preceding the Tertiary, generally given as from 144 million years b. p. to 65 million years b. p.. Also called Cre*tac"ic.

from The Century Dictionary and Cyclopedia

Chalky.

Found in chalk; found in strata of the cretaceous group.

n. [capitalized] In geology, the cretaceous group.

In botany: Chalky, or having chalk-glands, as in some species of Saxifraga.

Although an apparent explosion of dinosaur diversity occurred in the mid-Cretaceous, coinciding with the emergence of new groups e.g. neoceratopsians, ankylosaurid ankylosaurs, hadrosaurids and pachycephalosaurs, results from the first quantitative study of diversification applied to a new supertree of dinosaurs show that this apparent burst in dinosaurian diversity in the last 18 Myr of the Cretaceous is a sampling artefact.

Among the dozen specimens obtained were some fossil ammonites (a family of chambered shells) of genera which are found on other continents in certain formations classified as the Cretaceous system, and which occur neither above these formations nor below them.